The role of arachidonic acid oxygenation reactions in alveolar macrophages and their interaction with endothelial cells will be evaluated. The contribution of oxygen consumption to metabolic reactions catalyzed through cyclooxygenase and lipoxygenase pathways will be quantified in alveolar macrophages during phagocytic challenge. A variety of purturbants will be used to stimulate oxygen consumption including soluble agents, (FMLP, C5a, PMA, calcium ionophore A23187) and particles (opsonized zymosan, latex) with selective inhibitors of the cyclooxygenase and lipoxygenase pathway (indomethacin and ETYA). The interaction of alveolar macrophage attachment and aggregation with each other and with endothelial cells will be studied. The influence of the prostacyclin PGI2 generated from endothelial cells on alveolar macrophages attachment and aggregation responses will be evaluated. The levels of cyclic nucleotides will be evaluated at selective time points in alveolar macrophages with altered states of adherence and aggregation in response to PGI2 and to endothelial cell supernants derived from cell culture.